I've noticed that most of the LHs available here do not support BTS' modular loading. In particular the ones I want are for existing civs. How do I enable them in game? Thanks for the help

my marcus and constantine are modular but for existing civs you have to add an entry under the civilization for the leaderhead. my constantine has an edited rome as an example, but my marcus does not so you wouldh ave to add a marcus entry that is just a copy of constantine but change it to LEADER_XXXX (XXXX beinf the name in the leaderheadinfos.xml)